Rear axle of a passenger vehicle with five individual links

ABSTRACT

This invention relates to a rear axle of a vehicle, in particular a passenger vehicle, whose wheel mount is guided by five individual suspension links, at least two of which are coupled above the midpoint of the wheel and at least two are coupled essentially beneath the midpoint of the wheel, and the so-called steering rod as the fifth link is coupled behind the midpoint of the wheel (as seen in the direction of travel). To create a compact configuration, the two upper transverse links are situated in front of a spring element (as seen in the direction of travel) and/or a shock absorber element, which is located between the vehicle body and one of the lower suspension links. To improve the elastokinematic behavior, the steering rod is pitched at an angle of sweep with respect to the transverse direction of the vehicle, this angle being on the order of magnitude of 5° to 25°. The coupling points on the wheel mount side of the two upper suspension links and/or the lower suspension links are offset in height with respect to one another and neither the two upper suspension links nor the lower transverse link and the (lower) frame side bar describes a common plane. All the arms are preferably ultimately linked directly or indirectly to a rear axle mount which forms a supporting frame.

[0001] This invention relates to a rear axle of a motor vehicle, in particular a passenger vehicle, whose wheel mount is guided by five individual suspension links, two of which are linked above the midpoint of the wheel and at least two of which are linked essentially beneath the midpoint of the wheel, and where the so-called steering rod is linked above or below same, as seen from behind the midpoint of the wheel. Reference is made to German Patent Application DE 44 08 571 A1 for the technical background.

[0002] So-called five-link suspension axles are characterized in principle by optimum freedom of design, in particular with regard to the kinematic relationships, with special emphasis on the elastokinematics. However, problems arise due to the so-called design space management, i.e., how the available design space is utilized in the best possible way, taking into account all possible relative movements between the individual parts without having to accept unwanted vehicle handling responses as a result of these suspension link movements.

[0003] A rear axle as claimed in the preamble of Claim 1 will now be disclosed; it is characterized by a particularly advantageous utilization of the available design space (=object of the present invention).

[0004] This object is achieved by locating the two upper suspension links in front of a spring element (as seen in the direction of travel) and/or a shock absorber element, which is located between the vehicle body and one of the lower suspension links. Advantageous embodiments and refinements are characterized in the subclaims.

[0005] With the stated arrangement of the two upper suspension links, both of which are situated in front of a spring element (as seen in the direction of travel of the vehicle) and/or a shock absorber element on which the vehicle body is supported on the rear axle, these two suspension links can be designed to be relatively short. Thus the pivoting movements executed by these upper suspension links in spring deflection and rebounding of the vehicle body with respect to the axle are relatively minor, so this greatly reduces the possibility of a collision of one of these suspension links with a frame side bar, which is usually present in this area. Thus an essentially linear or at least slightly offset suspension link design is possible, resulting in a greater rigidity than is the case with a highly offset suspension link. A more rigid suspension link can then be mounted to advantage by means of simple, reliable rubber bearings and does not require complex bearings such as a ball-head bearing. Despite a frame side bar that is optimally designed (with regard to rigidity requirements), the upper transverse links configured according to this invention can thus also be designed to be absolutely in a straight line, thus also yielding kinematic advantages.

[0006] With regard to the steering rod, which is coupled to the wheel mount (both above and beneath) behind the midpoint of the wheel in the direction of travel of the vehicle and constitutes one of the three lower suspension links, it should be pointed out that due to this arrangement, the steering rod can be designed to be relatively long, which advantageously results in a lower tolerance sensitivity. Therefore, the cardanic forces and torsion to be absorbed in the corresponding joint (in particular between the steering rod and the wheel mount) are lower, which here again allows the use of simple rubber bearings (instead of ball-and-socket joints). Furthermore, a rear wheel steering can be implemented in a relatively simple manner with such a steering rod configuration.

[0007] If the steering rod runs in a plane parallel to the road surface so that it is pitched with respect to the transverse direction of the vehicle, i.e., if there is an angle of sweep of the steering rod (in a view of the rear axle from above), then a geometric position of the effective expansion axle is possible, producing an elastokinematic change in toe-in which has a neutral or stabilizing effect on the vehicle as a whole, and this is true in the driving case when forces act on the midpoint of the wheel between the wheel and the road surface as well as in the braking case when these forces act in the wheel contact area. This is true in particular when the absolute value of either the so-called tractive force lever arm or the so-called braking force lever arm is small and the absolute values of these two lever arms are different. In other words, this means that the expansion axle of the wheel suspension either runs almost through the midpoint of the wheel or almost through the midpoint of the wheel contact area, i.e., it is very close to one of these midpoints or it even passes through one of these midpoints. The so-called angle of sweep of the steering rod may then preferably be on the order of 3° to 25°.

[0008] With the features of Claim 3, namely that the coupling points of the two upper suspension links and/or the lower suspension links on the wheel mount side are offset in height in relation to one another, this also yields a gain in design space, because there is no collision between the screw elements or the like between adjacent suspension links and the wheel mount. In particular it is thus possible to couple the two upper transverse links as well as the lower transverse link and the (lower) frame side bar especially close to one another on the wheel mount, which is important, i.e., advantageous, in particular for the position of the effective expansion axle. Favorable kinematic relationships can be achieved if neither the two upper suspension links nor the lower transverse link and the (lower) frame side bar describes a common plane.

[0009] Claim 5 discloses a design of the steering rod which is advantageous in terms of manufacture and assembly. In most cases suspension links are linked at the end in a so-called double-shear linkage, i.e., a mounting bar, etc., which is provided on the wheel mount or on the vehicle body and/or a so-called carriage or axle mount, is in contact with the two opposite sides of the suspension link eye, etc. In particular with a steering rod that is designed to be relatively long and backswept, as proposed here (also because of the lack of tolerance sensitivity mentioned above), a so-called single-shear linkage is also possible on the carriage or axle mount, advantageously permitting a short design length of this carriage or axle mount. This single-shear linkage or screw connection on the carriage is preferably designed so that a structure-reinforcing connection (e.g., in the form of a welded spacer bushing) is provided between adjacent walls of a mount part of the carriage through which a bolt or screw element of the single-shear linkage is passed. This makes it possible to utilize the total flexural rigidity of the cross section of the mount part or carriage available at this point for a single-shear linkage connection.

[0010] As is essentially known, all the suspension links of a rear axle according to this invention may ultimately be linked directly or indirectly to a rear axle mount forming a supporting frame, thus simplifying in particular assembly of the entire axle unit. This and other advantageous features are also derived from the following description of a preferred exemplary embodiment, of which FIG. 1 shows a three-dimensional view, while FIG. 2 shows a top view and FIG. 3 shows a view from the rear, each illustrating the left half as seen in the direction of travel of an inventive rear axle for a passenger vehicle. FIG. 4 also shows a side view. All the features described in greater detail here may be essential to the invention.

[0011] A so-called rear axle mount or carriage is labeled with reference number 1 and is linked essentially via four fastening points to the vehicle body (not shown). Two wheel mounts 2, which are provided on both sides of the rear axle mount 1 (only the wheel mount 2 on the left side in the direction of travel FR is shown in all the figures), are each suspended on the rear axle mount 1 by way of five suspension links 11, 12, 13, 14, 15. Furthermore, an integrated rear differential 3 with a central suspension in the rear axle mount 1 can be seen, an output shaft 4 leading from this differential to the hubs, which are provided on the wheel mounts 2 but are not shown in detail here, for the rear wheels 7 (depicted abstractly in FIGS. 1 and 4) on the vehicle.

[0012] In addition to the elements already mentioned, a spring element 6 can be seen on both sides plus a shock absorber 5 next to it, by means of which the vehicle body (not shown) is supported essentially in the vertical direction on the rear axle, or more specifically on one of the lower transverse links, namely the so-called spring-shock-absorber-link 11. In this connection, it should be pointed out that the transverse direction of the vehicle is indicated by the arrow Q, while the longitudinal direction of the vehicle is equal to the direction of travel of the vehicle, which is represented by the arrow FR.

[0013] In addition to the (lower) spring-shock-absorber-link 11, another suspension link 12 is coupled beneath the midpoint M of the wheel (i.e., the midpoint line M of the wheel running horizontally) to the wheel mount 2, which is referred to as a frame side bar 12, although this frame side bar 12 also extends in the transverse direction Q of the vehicle. Finally, a third suspension link 13 here is also coupled to the wheel mount 2 beneath the midpoint M of the wheel, namely the so-called steering rod 13 (as an alternative, however, this steering rod 13 may also be at the level of or beneath the midpoint M of the wheel).

[0014] In addition to these suspension links 11, 12, 13, which have been mentioned so far and are coupled to the wheel mount 2, there are also two suspension links 14, 15 coupled to the wheel mount 2 above the midpoint M of the wheel. These two suspension links run in front of the spring element 6 and the shock absorber 5, as seen in the direction of travel FR, with the advantages indicated above. In the vertical direction V (see the view from the rear in FIG. 3), the coupling points 14 a, 15 a of these upper transverse links 14, 15 are situated one above the other and the same thing is also true of their coupling points on the rear axle mount 1, which are not shown separately, since the two upper suspension links 14, 15 run essentially parallel to one another in the vertical plane (corresponding to the plane of the drawing in FIG. 3). However, since they are not parallel to one another in the horizontal plane (see FIG. 2), these two upper arms 14, 15 do not describe a common plane.

[0015] The same thing is also true of the two lower suspension links 11, 12, namely the spring-shock-absorber-arm 11 and the frame side bar 12. The steering rod 13, which is also arranged as illustrated to achieve the advantages described above (in particular at an angle of sweep ν on the order of 10°), is situated as described above in detail. As this shows, the steering rod 13 has a single-shear linkage to the wheel mount 2 as well as the rear axle mount 1, namely concretely on a crossbar 1 a thereof, as shown best in FIGS. 2 and 3. A bolt 8 can be seen here passing through a rubber bearing, which is provided in the steering rod eye, and through the rear wall and front wall of the crossbar 1 a, which is designed as a hollow profile or a U-shaped profile, for example; in this area, a spacer bushing (not shown in the figure) may be welded between the front wall and the rear wall of the crossbar, with the bolt 8 running along the axle of the spacer bushing, reinforcing this single-shear linkage in an advantageous manner.

[0016] The rear axle described here is characterized by an extremely compact design with the advantages described above, and it should also be pointed out that a number of details, in particular those pertaining to the structure, can be designed in deviation from the exemplary embodiment presented here without going beyond the scope of the patent claims. 

1. Rear axle of a vehicle, in particular a passenger vehicle, whose wheel mount (2) is guided by five individual suspension links (11, 12, 13, 14, 15), at least two of which (14, 15) are coupled above the midpoint (M) of the wheel, and at least two of which (11, 12) are coupled essentially beneath the midpoint (M) of the wheel, and whereby the so-called steering rod (13) is coupled above or below the midpoint (M) of the wheel and behind same, as seen in the direction of travel (FR), characterized in that the two upper suspension links (14, 15) are situated in front of a spring element (6) (as seen in the direction of travel (FR)) and/or a shock absorber element (7), which is situated between the vehicle body and one of the lower suspension links (11, 12).
 2. Rear axle as claimed in claim 1, characterized in that the steering rod (13) is pitched at a so-called angle of sweep (ν) on the order of magnitude of 3° to 25° with respect to the transverse direction (Q) of the vehicle.
 3. Rear axle as claimed in claim 1 or 2, characterized in that the wheel mount-side coupling points (14 a, 15 a) of the two upper suspension links (14, 15) and/or the lower suspension links (11, 12, 13) are offset in height in relation to one another.
 4. Rear axle as claimed in any one of the preceding claims, characterized in that neither the two upper suspension links (14, 15) nor the lower transverse links (11) and the (lower) frame side bar (12) describes a common plane.
 5. Rear axle as claimed in any one of the preceding claims, characterized in that the steering rod (13) is coupled in a single-shear linkage to at least one end.
 6. Rear axle as claimed in any one of the preceding claims, characterized in that all the suspension links (11-15) are ultimately linked directly or indirectly to a rear axle mount (1) which forms a supporting frame. 